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  • Which shopping cart / ecommerce platform to choose?

    - by fabien7474
    I need to build an ecommerce website within a tight budget and schedule. Of course, I have never done that before, so I have googled out what my solutions are and I have concluded that the following were not valid candidates anymore : Magento : Steep learning curve osCommerce : old, bad design, buggy and not user-friendly Zencart, CRE Loaded, CubeCart : based on osCommerce Virtuemart, uberCart, eCart : based on CMS (Joomal, Drupal, WordPress) that is not necessary for my use-case So I finally narrowed down my choices to these solutions : PrestaShop : easy-to-use, great templating engine (smarty) but many modules are not free buy yet indispensable OpenCart : security issues and not a great support from the main developer. See here and here. So, as you can see, I am a little bit confused and if you can help me choosing an easy-to-use, lightweight and cheap (not-necessarily free) ecommerce solution, I would really appreciate. By the way, I am a Java/Grails programmer but I am also familiar with PHP and .NET. (not with Python or Ruby/Rails) EDIT: It seems that this question is more appropriate for the Webmaster StackExchange site. So please move this question to where it belongs (I cannot do that) instead of downvoting it. BTW, I have found out a question quite similar on SO (http://stackoverflow.com/questions/3315638/php-ecommerce-system-which-one-is-easiest-to-modify) which is quite popular.

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  • How to choose size for a cloud server (rackspace)

    - by Emil
    We're going to test the rackspace cloud next week to see how it's working with our web app. It's a LAMP environment with a lot of MySQL databases. How do I choose the "right" server size? On Rackspace I can choose slices with the memory of 256, 512, 1024, 2048, 4096 etc. Right now we don't have a lot of traffic (approx. 1000 visitors/day) but I thought the whole "cloud" idea was to not be limited and auto scale. Update: What I'm looking for is now a specification of what I need. I know it's too complex. I'm looking for examples, case studies etc. It would be interesting to hear something like "Yes we're serving 10 000 daily requests without spikes on a LAMP stack with only one slice on with 2 GB RAM".

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  • Why Are Minimized Programs Often Slow to Open Again?

    - by Jason Fitzpatrick
    It seems particularly counterintuitive: you minimize an application because you plan on returning to it later and wish to skip shutting the application down and restarting it later, but sometimes maximizing it takes even longer than launching it fresh. What gives? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. The Question SuperUser reader Bart wants to know why he’s not saving any time with application minimization: I’m working in Photoshop CS6 and multiple browsers a lot. I’m not using them all at once, so sometimes some applications are minimized to taskbar for hours or days. The problem is, when I try to maximize them from the taskbar – it sometimes takes longer than starting them! Especially Photoshop feels really weird for many seconds after finally showing up, it’s slow, unresponsive and even sometimes totally freezes for minute or two. It’s not a hardware problem as it’s been like that since always on all on my PCs. Would I also notice it after upgrading my HDD to SDD and adding RAM (my main PC holds 4 GB currently)? Could guys with powerful pcs / macs tell me – does it also happen to you? I guess OSes somehow “focus” on active software and move all the resources away from the ones that run, but are not used. Is it possible to somehow set RAM / CPU / HDD priorities or something, for let’s say, Photoshop, so it won’t slow down after long period of inactivity? So what is the deal? Why does he find himself waiting to maximize a minimized app? The Answer SuperUser contributor Allquixotic explains why: Summary The immediate problem is that the programs that you have minimized are being paged out to the “page file” on your hard disk. This symptom can be improved by installing a Solid State Disk (SSD), adding more RAM to your system, reducing the number of programs you have open, or upgrading to a newer system architecture (for instance, Ivy Bridge or Haswell). Out of these options, adding more RAM is generally the most effective solution. Explanation The default behavior of Windows is to give active applications priority over inactive applications for having a spot in RAM. When there’s significant memory pressure (meaning the system doesn’t have a lot of free RAM if it were to let every program have all the RAM it wants), it starts putting minimized programs into the page file, which means it writes out their contents from RAM to disk, and then makes that area of RAM free. That free RAM helps programs you’re actively using — say, your web browser — run faster, because if they need to claim a new segment of RAM (like when you open a new tab), they can do so. This “free” RAM is also used as page cache, which means that when active programs attempt to read data on your hard disk, that data might be cached in RAM, which prevents your hard disk from being accessed to get that data. By using the majority of your RAM for page cache, and swapping out unused programs to disk, Windows is trying to improve responsiveness of the program(s) you are actively using, by making RAM available to them, and caching the files they access in RAM instead of the hard disk. The downside of this behavior is that minimized programs can take a while to have their contents copied from the page file, on disk, back into RAM. The time increases the larger the program’s footprint in memory. This is why you experience that delay when maximizing Photoshop. RAM is many times faster than a hard disk (depending on the specific hardware, it can be up to several orders of magnitude). An SSD is considerably faster than a hard disk, but it is still slower than RAM by orders of magnitude. Having your page file on an SSD will help, but it will also wear out the SSD more quickly than usual if your page file is heavily utilized due to RAM pressure. Remedies Here is an explanation of the available remedies, and their general effectiveness: Installing more RAM: This is the recommended path. If your system does not support more RAM than you already have installed, you will need to upgrade more of your system: possibly your motherboard, CPU, chassis, power supply, etc. depending on how old it is. If it’s a laptop, chances are you’ll have to buy an entire new laptop that supports more installed RAM. When you install more RAM, you reduce memory pressure, which reduces use of the page file, which is a good thing all around. You also make available more RAM for page cache, which will make all programs that access the hard disk run faster. As of Q4 2013, my personal recommendation is that you have at least 8 GB of RAM for a desktop or laptop whose purpose is anything more complex than web browsing and email. That means photo editing, video editing/viewing, playing computer games, audio editing or recording, programming / development, etc. all should have at least 8 GB of RAM, if not more. Run fewer programs at a time: This will only work if the programs you are running do not use a lot of memory on their own. Unfortunately, Adobe Creative Suite products such as Photoshop CS6 are known for using an enormous amount of memory. This also limits your multitasking ability. It’s a temporary, free remedy, but it can be an inconvenience to close down your web browser or Word every time you start Photoshop, for instance. This also wouldn’t stop Photoshop from being swapped when minimizing it, so it really isn’t a very effective solution. It only helps in some specific situations. Install an SSD: If your page file is on an SSD, the SSD’s improved speed compared to a hard disk will result in generally improved performance when the page file has to be read from or written to. Be aware that SSDs are not designed to withstand a very frequent and constant random stream of writes; they can only be written over a limited number of times before they start to break down. Heavy use of a page file is not a particularly good workload for an SSD. You should install an SSD in combination with a large amount of RAM if you want maximum performance while preserving the longevity of the SSD. Use a newer system architecture: Depending on the age of your system, you may be using an out of date system architecture. The “system architecture” is generally defined as the “generation” (think generations like children, parents, grandparents, etc.) of the motherboard and CPU. Newer generations generally support faster I/O (input/output), better memory bandwidth, lower latency, and less contention over shared resources, instead providing dedicated links between components. For example, starting with the “Nehalem” generation (around 2009), the Front-Side Bus (FSB) was eliminated, which removed a common bottleneck, because almost all system components had to share the same FSB for transmitting data. This was replaced with a “point to point” architecture, meaning that each component gets its own dedicated “lane” to the CPU, which continues to be improved every few years with new generations. You will generally see a more significant improvement in overall system performance depending on the “gap” between your computer’s architecture and the latest one available. For example, a Pentium 4 architecture from 2004 is going to see a much more significant improvement upgrading to “Haswell” (the latest as of Q4 2013) than a “Sandy Bridge” architecture from ~2010. Links Related questions: How to reduce disk thrashing (paging)? Windows Swap (Page File): Enable or Disable? Also, just in case you’re considering it, you really shouldn’t disable the page file, as this will only make matters worse; see here. And, in case you needed extra convincing to leave the Windows Page File alone, see here and here. Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.     

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  • Deleting a row from self-referencing table

    - by Jake Rutherford
    Came across this the other day and thought “this would be a great interview question!” I’d created a table with a self-referencing foreign key. The application was calling a stored procedure I’d created to delete a row which caused but of course…a foreign key exception. You may say “why not just use a the cascade delete option?” Good question, easy answer. With a typical foreign key relationship between different tables which would work. However, even SQL Server cannot do a cascade delete of a row on a table with self-referencing foreign key. So, what do you do?…… In my case I re-wrote the stored procedure to take advantage of recursion:   -- recursively deletes a Foo ALTER PROCEDURE [dbo].[usp_DeleteFoo]      @ID int     ,@Debug bit = 0    AS     SET NOCOUNT ON;     BEGIN TRANSACTION     BEGIN TRY         DECLARE @ChildFoos TABLE         (             ID int         )                 DECLARE @ChildFooID int                        INSERT INTO @ChildFoos         SELECT ID FROM Foo WHERE ParentFooID = @ID                 WHILE EXISTS (SELECT ID FROM @ChildFoos)         BEGIN             SELECT TOP 1                 @ChildFooID = ID             FROM                 @ChildFoos                             DELETE FROM @ChildFoos WHERE ID = @ChildFooID                         EXEC usp_DeleteFoo @ChildFooID         END                                    DELETE FROM dbo.[Foo]         WHERE [ID] = @ID                 IF @Debug = 1 PRINT 'DEBUG:usp_DeleteFoo, deleted - ID: ' + CONVERT(VARCHAR, @ID)         COMMIT TRANSACTION     END TRY     BEGIN CATCH         ROLLBACK TRANSACTION         DECLARE @ErrorMessage VARCHAR(4000), @ErrorSeverity INT, @ErrorState INT         SELECT @ErrorMessage = ERROR_MESSAGE(), @ErrorSeverity = ERROR_SEVERITY(), @ErrorState = ERROR_STATE()         IF @ErrorState <= 0 SET @ErrorState = 1         INSERT INTO ErrorLog(ErrorNumber,ErrorSeverity,ErrorState,ErrorProcedure,ErrorLine,ErrorMessage)         VALUES(ERROR_NUMBER(), @ErrorSeverity, @ErrorState, ERROR_PROCEDURE(), ERROR_LINE(), @ErrorMessage)         RAISERROR (@ErrorMessage, @ErrorSeverity, @ErrorState)     END CATCH   This procedure will first determine any rows which have the row we wish to delete as it’s parent. It then simply iterates each child row calling the procedure recursively in order to delete all ancestors before eventually deleting the row we wish to delete.

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  • BizTalk and SQL: Alternatives to the SQL receive adapter. Using Msmq to receive SQL data

    - by Leonid Ganeline
    If we have to get data from the SQL database, the standard way is to use a receive port with SQL adapter. SQL receive adapter is a solicit-response adapter. It periodically polls the SQL database with queries. That’s only way it can work. Sometimes it is undesirable. With new WCF-SQL adapter we can use the lightweight approach but still with the same principle, the WCF-SQL adapter periodically solicits the database with queries to check for the new records. Imagine the situation when the new records can appear in very broad time limits, some - in a second interval, others - in the several minutes interval. Our requirement is to process the new records ASAP. That means the polling interval should be near the shortest interval between the new records, a second interval. As a result the most of the poll queries would return nothing and would load the database without good reason. If the database is working under heavy payload, it is very undesirable. Do we have other choices? Sure. We can change the polling to the “eventing”. The good news is the SQL server could issue the event in case of new records with triggers. Got a new record –the trigger event is fired. No new records – no the trigger events – no excessive load to the database. The bad news is the SQL Server doesn’t have intrinsic methods to send the event data outside. For example, we would rather use the adapters that do listen for the data and do not solicit. There are several such adapters-listeners as File, Ftp, SOAP, WCF, and Msmq. But the SQL Server doesn’t have methods to create and save files, to consume the Web-services, to create and send messages in the queue, does it? Can we use the File, FTP, Msmq, WCF adapters to get data from SQL code? Yes, we can. The SQL Server 2005 and 2008 have the possibility to use .NET code inside SQL code. See the SQL Integration. How it works for the Msmq, for example: ·         New record is created, trigger is fired ·         Trigger calls the CLR stored procedure and passes the message parameters to it ·         The CLR stored procedure creates message and sends it to the outgoing queue in the SQL Server computer. ·         Msmq service transfers message to the queue in the BizTalk Server computer. ·         WCF-NetMsmq adapter receives the message from this queue. For the File adapter the idea is the same, the CLR stored procedure creates and stores the file with message, and then the File adapter picks up this file. Using WCF-NetMsmq adapter to get data from SQL I am describing the full set of the deployment and development steps for the case with the WCF-NetMsmq adapter. Development: 1.       Create the .NET code: project, class and method to create and send the message to the MSMQ queue. 2.       Create the SQL code in triggers to call the .NET code. Installation and Deployment: 1.       SQL Server: a.       Register the CLR assembly with .NET (CLR) code b.      Install the MSMQ Services 2.       BizTalk Server: a.       Install the MSMQ Services b.      Create the MSMQ queue c.       Create the WCF-NetMsmq receive port. The detailed description is below. Code .NET code … using System.Xml; using System.Xml.Linq; using System.Xml.Serialization;   //namespace MyCompany.MySolution.MyProject – doesn’t work. The assembly name is MyCompany.MySolution.MyProject // I gave up with the compound namespace. Seems the CLR Integration cannot work with it L. Maybe I’m wrong.     public class Event     {         static public XElement CreateMsg(int par1, int par2, int par3)         {             XNamespace ns = "http://schemas.microsoft.com/Sql/2008/05/TypedPolling/my_storedProc";             XElement xdoc =                 new XElement(ns + "TypedPolling",                     new XElement(ns + "TypedPollingResultSet0",                         new XElement(ns + "TypedPollingResultSet0",                             new XElement(ns + "par1", par1),                             new XElement(ns + "par2", par2),                             new XElement(ns + "par3", par3),                         )                     )                 );             return xdoc;         }     }   //////////////////////////////////////////////////////////////////////// … using System.ServiceModel; using System.ServiceModel.Channels; using System.Transactions; using System.Data; using System.Data.Sql; using System.Data.SqlTypes;   public class MsmqHelper {     [Microsoft.SqlServer.Server.SqlProcedure]     // msmqAddress as "net.msmq://localhost/private/myapp.myqueue";     public static void SendMsg(string msmqAddress, string action, int par1, int par2, int par3)     {         using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Suppress))         {             NetMsmqBinding binding = new NetMsmqBinding(NetMsmqSecurityMode.None);             binding.ExactlyOnce = true;             EndpointAddress address = new EndpointAddress(msmqAddress);               using (ChannelFactory<IOutputChannel> factory = new ChannelFactory<IOutputChannel>(binding, address))             {                 IOutputChannel channel = factory.CreateChannel();                 try                 {                     XElement xe = Event.CreateMsg(par1, par2, par3);                     XmlReader xr = xe.CreateReader();                     Message msg = Message.CreateMessage(MessageVersion.Default, action, xr);                     channel.Send(msg);                     //SqlContext.Pipe.Send(…); // to test                 }                 catch (Exception ex)                 { …                 }             }             scope.Complete();         }     }   SQL code in triggers   -- sp_SendMsg was registered as a name of the MsmqHelper.SendMsg() EXEC sp_SendMsg'net.msmq://biztalk_server_name/private/myapp.myqueue', 'Create', @par1, @par2, @par3   Installation and Deployment On the SQL Server Registering the CLR assembly 1.       Prerequisites: .NET 3.5 SP1 Framework. It could be the issue for the production SQL Server! 2.       For more information, please, see the link http://nielsb.wordpress.com/sqlclrwcf/ 3.       Copy files: >copy “\Windows\Microsoft.net\Framework\v3.0\Windows Communication Foundation\Microsoft.Transactions.Bridge.dll” “\Program Files\Reference Assemblies\Microsoft\Framework\v3.0 \Microsoft.Transactions.Bridge.dll” If your machine is a 64-bit, run two commands: >copy “\Windows\Microsoft.net\Framework\v3.0\Windows Communication Foundation\Microsoft.Transactions.Bridge.dll” “\Program Files (x86)\Reference Assemblies\Microsoft\Framework\v3.0 \Microsoft.Transactions.Bridge.dll” >copy “\Windows\Microsoft.net\Framework64\v3.0\Windows Communication Foundation\Microsoft.Transactions.Bridge.dll” “\Program Files\Reference Assemblies\Microsoft\Framework\v3.0 \Microsoft.Transactions.Bridge.dll” 4.       Execute the SQL code to register the .NET assemblies: -- For x64 OS: CREATE ASSEMBLY SMdiagnostics AUTHORIZATION dbo FROM 'C:\Windows\Microsoft.NET\Framework\v3.0\Windows Communication Foundation\SMdiagnostics.dll' WITH permission_set = unsafe CREATE ASSEMBLY [System.Web] AUTHORIZATION dbo FROM 'C:\Windows\Microsoft.NET\Framework64\v2.0.50727\System.Web.dll' WITH permission_set = unsafe CREATE ASSEMBLY [System.Messaging] AUTHORIZATION dbo FROM 'C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Messaging.dll' WITH permission_set = unsafe CREATE ASSEMBLY [System.ServiceModel] AUTHORIZATION dbo FROM 'C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\v3.0\System.ServiceModel.dll' WITH permission_set = unsafe CREATE ASSEMBLY [System.Xml.Linq] AUTHORIZATION dbo FROM 'C:\Program Files\Reference Assemblies\Microsoft\Framework\v3.5\System.Xml.Linq.dll' WITH permission_set = unsafe   -- For x32 OS: --CREATE ASSEMBLY SMdiagnostics AUTHORIZATION dbo FROM 'C:\Windows\Microsoft.NET\Framework\v3.0\Windows Communication Foundation\SMdiagnostics.dll' WITH permission_set = unsafe --CREATE ASSEMBLY [System.Web] AUTHORIZATION dbo FROM 'C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Web.dll' WITH permission_set = unsafe --CREATE ASSEMBLY [System.Messaging] AUTHORIZATION dbo FROM 'C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Messaging.dll' WITH permission_set = unsafe --CREATE ASSEMBLY [System.ServiceModel] AUTHORIZATION dbo FROM 'C:\Program Files\Reference Assemblies\Microsoft\Framework\v3.0\System.ServiceModel.dll' WITH permission_set = unsafe 5.       Register the assembly with the external stored procedure: CREATE ASSEMBLY [HelperClass] AUTHORIZATION dbo FROM ’<FilePath>MyCompany.MySolution.MyProject.dll' WITH permission_set = unsafe where the <FilePath> - the path of the file on this machine! 6. Create the external stored procedure CREATE PROCEDURE sp_SendMsg (        @msmqAddress nvarchar(100),        @Action NVARCHAR(50),        @par1 int,        @par2 int,        @par3 int ) AS EXTERNAL NAME HelperClear.MsmqHelper.SendMsg   Installing the MSMQ Services 1.       Check if the MSMQ service is NOT installed. To check:  Start / Administrative Tools / Computer Management, on the left pane open the “Services and Applications”, search to the “Message Queuing”. If you cannot see it, follow next steps. 2.       Start / Control Panel / Programs and Features 3.       Click “Turn Windows Features on or off” 4.       Click Features, click “Add Features” 5.       Scroll down the feature list; open the “Message Queuing” / “Message Queuing Services”; and check the “Message Queuing Server” option  6.       Click Next; Click Install; wait to the successful finish of the installation Creating the MSMQ queue We don’t need to create the queue on the “sender” side. On the BizTalk Server Installing the MSMQ Services The same is as for the SQL Server. Creating the MSMQ queue 1.       Start / Administrative Tools / Computer Management, on the left pane open the “Services and Applications”, open the “Message Queuing”, and open the “Private Queues”. 2.       Right-click the “Private Queues”; choose New; choose “Private Queue”. 3.       Type the Queue name as ’myapp.myqueue'; check the “Transactional” option. Creating the WCF-NetMsmq receive port I will not go through this step in all details. It is straightforward. URI for this receive location should be 'net.msmq://localhost/private/myapp.myqueue'. Notes ·         The biggest problem is usually on the step the “Registering the CLR assembly”. It is hard to predict where are the assemblies from the assembly list, what version should be used, x86 or x64. It is pity of such “rude” integration of the SQL with .NET. ·         In couple cases the new WCF-NetMsmq port was not able to work with the queue. Try to replace the WCF- NetMsmq port with the WCF-Custom port with netMsmqBinding. It was working fine for me. ·         To test how messages go through the queue you can turn on the Journal /Enabled option for the queue. I used the QueueExplorer utility to look to the messages in Journal. The Computer Management can also show the messages but it shows only small part of the message body and in the weird format. The QueueExplorer can do the better job; it shows the whole body and Xml messages are in good color format.

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  • What tools should every programmer know?

    - by acidzombie24
    What are some tools every programmer know about? Some examples i thought were Source control. (No explanation needed) Profiler. Many could go without but its good to know how to use one when the occasion arise What else? I was thinking a bug report software but i havent used one so i wasnt sure. Should programmers know how to use TRAC? I remember in the past a person telling me if i was making a shared library i should know (Some Name) which generates docs from the source (in that case C++). What was that called and what else should i know about? -edit- what about team management software? any software you could not live without in a specific project would be a good mention. I'll also mention i use VMs frequently during the prototype or end phase to see if there are any issues on a clean XP or linux distro and if i forgot anything in my redistribution. I cant imagine the end/release and testing phase of a project without a VM.

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  • monitoring TCP/IP performance on Solaris

    - by Andy Faibishenko
    I am trying to tune a high message traffic system running on Solaris. The architecture is a large number (600) of clients which connect via TCP to a big Solaris server and then send/receive relatively small messages (.5 to 1K payload) at high rates. The goal is to minimize the latency of each message processed. I suspect that the TCP stack of the server is getting overwhelmed by all the traffic. What are some commands/metrics that I can use to confirm this, and in case this is true, what is the best way to alleviate this bottleneck?

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  • Is my disk hot or not?

    - by adriangrigore
    I am trying to figure out the temperature of my dedicated server's harddisk. For this purpose, I've downloaded HDTune to monitor the S.M.A.R.T. Status. The problem is that the current temperature for "C2 Temperature" is 73 degrees celsius, but the little thermometer on top of the window shows 27 degrees celsius. See this screenshot: http://screencast.com/t/OGJhZGIxND Another monitoring software (Anfibia Reactor) shows similar behavior: Disk temperature is around 30 degrees, but it says that the disk is too hot. So, is my disk hot or not? Since this is a dedicated server, I can't just open the case and put a thumb on it.

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  • "Programming error" exceptions - Is my approach sound?

    - by Medo42
    I am currently trying to improve my use of exceptions, and found the important distinction between exceptions that signify programming errors (e.g. someone passed null as argument, or called a method on an object after it was disposed) and those that signify a failure in the operation that is not the caller's fault (e.g. an I/O exception). As far as I understand, it makes little sense for an immediate caller to actually handle programming error exceptions, he should instead assure that the preconditions are met. Only "outer" exception handlers at task boundaries should catch them, so they can keep the system running if a task fails. In order to ensure that client code can cleanly catch "failure" exceptions without catching error exceptions by mistake, I create my own exception classes for all failure exceptions now, and document them in the methods that throw them. I would make them checked exceptions in Java. Now I have a few questions: Before, I tried to document all exceptions that a method could throw, but that sometimes creates an unwiedly list that needs to be documented in every method up the call chain until you can show that the error won't happen. Instead, I document the preconditions in the summary / parameter descriptions and don't even mention what happens if they are not met. The idea is that people should not try to catch these exceptions explicitly anyway, so there is no need to document their types. Would you agree that this is enough? Going further, do you think all preconditions even need to be documented for every method? For example, calling methods in IDisposable objects after calling Dispose is an error, but since IDisposable is such a widely used interface, can I just assume a programmer will know this? A similar case is with reference type parameters where passing null makes no conceivable sense: Should I document "non-null" anyway? IMO, documentation should only cover things that are not obvious, but I am not sure where "obvious" ends.

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  • Adding complexity by generalising: how far should you go?

    - by marcog
    Reference question: http://stackoverflow.com/questions/4303813/help-with-interview-question The above question asked to solve a problem for an NxN matrix. While there was an easy solution, I gave a more general solution to solve the more general problem for an NxM matrix. A handful of people commented that this generalisation was bad because it made the solution more complex. One such comment is voted +8. Putting aside the hard-to-explain voting effects on SO, there are two types of complexity to be considered here: Runtime complexity, i.e. how fast does the code run Code complexity, i.e. how difficult is the code to read and understand The question of runtime complexity is something that requires a better understanding of the input data today and what it might look like in the future, taking the various growth factors into account where necessary. The question of code complexity is the one I'm interested in here. By generalising the solution, we avoid having to rewrite it in the event that the constraints change. However, at the same time it can often result in complicating the code. In the reference question, the code for NxN is easy to understand for any competent programmer, but the NxM case (unless documented well) could easily confuse someone coming across the code for the first time. So, my question is this: Where should you draw the line between generalising and keeping the code easy to understand?

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  • Unable to drag and drop / select multiple with mouse

    - by J. Scott Elblein
    I'm running into a perplexing issue with Windows 8 Pro x64, where randomly I'm unable to drag to select multiple files (i.e. in Explorer or Directory Opus). I've also noticed that a similar issue happens when I'm running for example Photoshop or Illustrator and can't drag to select multiple layers, or drag to do some other things in them. it happens randomly and have found no way to reliably reproduce it, but it happens VERY frequently. I have read some tips saying pressing the ESC button usually fixes the issue, but it doesn't in my case. From what I understand, it's probably due to some other process locking the drag feature somehow, but I've not found a way to tell which process is the perp; I've even tried using unlock software on files when I'm suddenly unable to drag and I'm told by it that nothing is locking it. Anyone have any ideas?

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  • XEN disk mapping problem under opensolaris

    - by Louis
    I have a system with two harddisks, i wanted to use the simplicity of ZFS for my file server and i also need to run a linux. I choosed XEN virtualization for that, supported on both system. My GRUB is well configured and i can boot both system. I would like is to run both system with solaris as a dom0 and the debian installed on the 2nd HD as a virtual machine. My problem is that i want to use the partitions of my 1st harddisk (sda1 under linux) and it does not work. I didn't find my use case on the web- Here is my Opensolaris device name of this partition : /dev/rdsk/c7d0p1 But when i use : disk = [ 'phy:rdsk/c7d0p1,sda1,w' ] as a disk mapping in my XEN configuration file i have the error : Error: Device 2049 (vbd) could not be connected. error: "rdsk/c7d0p1" is not a valid block device. I am "lost".

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  • concatenate files including path in header - path contains spaces

    - by manolo
    I have to concatenate a number of files in a directory structure which contains spaces in the folder names looking like this: ./CH 0000100014/A10/11XT/11xt#001.csv find . -name "*.csv" -type f -print0 | xargs -0 cat > allmycsv.txt does the job, however now I need to include the information contained in the path, i.e. CH 0000100014/A10/11XT as a header of each inputfile to cat. find . -name "*.csv" -type f -print0 | xargs -0 -I % sh -c 'echo %; cat %' >allmycsv.txt would do the job, if I had no spaces in the path, but in my case, cat does not get along with the space in the path name. Is there a way out? Cheers, E P.S. I am working on bash on OSX

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  • "Don't do programming after a few years of starting career" Is this a fair advice?

    - by Muhammad Yasir
    I am a little experienced developer having around 5 years experience in PHP and somewhat less in Java, C# and trying to learn some Python now a days. Since the start of my career as a programmer I have been told every now and then by fellow programmers that programming is suitable for a few early years of carrier (most of them take it as 5 years) and that one must change the direction after it. The reason they present is that headaches and pressures associated with programming. They also say that programmers are less social and don't usually like to give time to their families etc. and specially "Oh come on, you can not do programming in your entire life!" I am somewhat confused here and need to ask others about it. If I leave programming then what do I do?! I guess teaching may be a good option in this case but it will require to first earn a PhD degree perhaps. It may also be noteworthy that in my country (Pakistan) the life of a programmer is not very good in that normally they must give 2-3 extra hours in office to accomplish urgent programming tasks. I have a sense that situation is somewhat similar in other countries and regions as well. So the question is, do you think it is a fair advice to change career from programming to something else after spending 5 years in this field? Thanks for sharing thoughts!

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  • Hypertransport sync flood error

    - by Carl B
    What is it? And what causes it? Is it only for uncorrectable DIMM Errors(Troubleshooting DIMM errors)? When an UCE occurs, the memory controller causes an immediate reboot of the system. During reboot, the BIOS checks the Machine Check registers and determines that the previous reboot was due to an UCE, then reports this in POST after the memtest stage: A Hypertransport Sync Flood occurred on last boot 3 BIOS reports this event in the service processor’s system event log (SEL) as shown in the sample IPMItool output There are what seems to be some suggested answers to include Bad Caps Bios verisons (happens in one version not the other) Graphics card issues Lack of power to the CPU The list of possible generators seems to target everything but the computer case. System Specs: Windows Home Premium 64 Motherboard - MSI790FX-GD70 (MS7577) / Bios v 1.9 (American Megatrensa Inc) Ram - Patriot G Series ‘Sector 5’ Edition 4GB DDR3 1600 CPU - AMD Phenom II X2 555 Black Edition Callisto 3.2GHz Socket AM3 80W (Note: unlocked 2 cores CPU Z ids it as phenom II x4 B55) Graphics - 2 x Radeon 5750 in crossfire PSU - ABS 900w HDDs - 2 Seagate 1.5 TB Sata SSD - 1 OCZ 120 GB Vertex Plus R2

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  • Unable to mount external hard drive - Damaged file system and MFT

    - by Khalifa Abbas Lame
    I get the following error when i try to mount my external hard drive. UNABLE TO MOUNT Error mounting /dev/sdc1 at /media/khalibloo/Khalibloo2: Command-line `mount -t "ntfs" -o "uhelper=udisks2,nodev,nosuid,uid=1000,gid=1000,dmask=0077,fmask=0177" "/dev/sdc1" "/media/khalibloo/Khalibloo2"' exited with non-zero exit status 13: ntfs_attr_pread_i: ntfs_pread failed: Input/output error Failed to read of MFT, mft=6 count=1 br=-1: Input/output error Failed to open inode FILE_Bitmap: Input/output error Failed to mount '/dev/sdc1': Input/output error NTFS is either inconsistent, or there is a hardware fault, or it's a SoftRAID/FakeRAID hardware. In the first case run chkdsk /f on Windows then reboot into Windows twice. The usage of the /f parameter is very important! If the device is a SoftRAID/FakeRAID then first activate it and mount a different device under the /dev/mapper/ directory, (e.g. /dev/mapper/nvidia_eahaabcc1). Please see the 'dmraid' documentation for more details. It doesn't mount on windows either: "I/O Device error" it's an ntfs hard drive with a single partition Of course, i tried chkdsk /f. it reported several file segments as unreadable, but didn't say whether it fixed them or not (apparently not). also tried with the /b flag. ntfsfix reported the volume as corrupt. TestDisk was able to fix a small error with the partition table by adding the "80" flag for the active (only) partition. TestDisk also confirmed that the boot sector was fine and it matched the backup. However, when attempting to repair the MFT, it couldn't read the MFT. It also couldn't list the files on the hard drive. It says file system may be damaged. Active@ also shows that MFT is missing or corrupt. So how do i fix the file system? or the MFT?

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  • How to change XFCE to LXDE?

    - by kurp
    I've just installed LinuxMint XFCE, which seems to be still a bit to heavy for my hardware. Thus, I'm thinking about LXDE installation and wonder if a new Linux installation is necessary/advised in such case. The question is: how to switch easily? The additional questions are: a) is it necessary to remove the XFCE packages or both DEs may be installed at the same time? b) is there any way to simply switch between DEs (i.e. have both DEs available and boot with DE selected each time)? c) are there any performance consequences of having more than one DE installed? it means: is clean LXDE installation faster than Linux with 2 separate desktops?

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  • Problems installing Ubuntu on a vaio with SSD, GRUB installation failure

    - by Alberto
    I have installed and used Ubuntu in several computers. But now I have a problem that I don't know how to solve. I have a Vaio (Product name: vpcz13c5e), it has a SSD 128gb. I decided to install Ubuntu (12.04, but I have tried older versions as well). Firstly, I tested with live USB, and everything was fine, so I decided go for the complete installation. Then everything went as follows: I chose to use the whole disk (first option, formatting everything). I got a message Executing 'grub-install' /deb/sdb failed. This is a fatal error After clicking ok I got another window with 3 options: the first offers different devices to install the bootloader on (I tried all of them and none works). Second option: Continue without a bootloader. In that case I got You will need to manually install a bootloader in order to start Ubuntu The third option is Cancel the installation. So, I chose Continue without a bootloader. Then I restart the computer (with the Live cd) and in a terminal type sudo fdisk -l but I obtain fdisk: unable to seek on /dev/sda: Invalid argument What can I do? any help will be appreciated.

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  • When does the "Do One Thing" paradigm become harmful?

    - by Petr
    For the sake of argument here's a sample function that prints contents of a given file line-by-line. Version 1: void printFile(const string & filePath) { fstream file(filePath, ios::in); string line; while (file.good()) { getline(file, line); cout << line << endl; } } I know it is recommended that functions do one thing at one level of abstraction. To me, though code above does pretty much one thing and is fairly atomic. Some books (such as Robert C. Martin's Clean Code) seem to suggest breaking the above code into separate functions. Version 2: void printLine(const string & line) { cout << line << endl; } void printLines(fstream & file) { string line; while (file.good()) { getline(file, line); printLine(line); } } void printFile(const string & filePath) { fstream file(filePath, ios::in); printLines(file); } I understand what they want to achieve (open file / read lines / print line), but isn't it a bit of overkill? The original version is simple and in some sense already does one thing - prints a file. The second version will lead to a large number of really small functions which may be far less legible than the first version. Wouldn't it be, in this case, better to have the code at one place? At which point does the "Do One Thing" paradigm become harmful?

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  • Possible to use LVM partitions inside a vmbuilder created KVM virtual machine?

    - by Tauren
    I have an Ubuntu 9.10 host system with LVM partitions running KVM. I've been creating VMs using vmbuilder using LVM partitions for each VM instead of files for the VMs. When I configure a VM using vmbuilder --part, the partitions in the file I'm using are created as regular partitions (sda1, sda2, etc.). What I'd like to do is use LVM inside of the VM in case I need to resize the partitions at some point. But I don't see any options for doing that using the vmbuilder tool. It seems like this might be a common request to avoid using kpartx, etc. Is there something I'm missing, or is this just not possible with vmbuilder?

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  • Get a culture specific list of month names

    - by erwin21
    A while ago I found a clever way to retrieve a dynamic culture specific list of months names in C# with LINQ. 1: var months = Enumerable.Range(1, 12) 2: .Select(i => new 3: { 4: Month = i.ToString(), 5: MonthName = new DateTime(1, i, 1).ToString("MMMM") 6: }) 7: .ToList(); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } It’s fairly simple, for a range of numbers from 1 to 12 a DateTime object is created (year and day doesn’t matter in this case), then the date time object formatted to a full month name with ToString(“MMMM”). In this example an anonymous object is created with a Month and MonthName property. You can use this solution to populate your dropdown list with months or to display a user friendly month name.

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  • MVC Validation with ModelState.isValid through a wizard

    - by Emmanuel TOPE
    I'm working on a small educational project on MVC 3, and I'm facing a small problem, when attempting to handle validation in my application through a wizard. I tried to get benefit from the ability of MVC3 to deliver content of a different view using the same URL, when handling an [HttpPost] method on a page. I my case,my main model's class contains about ten [Required] properties, that I would like to expose through a small wizard in 3 steps , So I want that the user may be able to enter his personal informations in the first step, then respond to some questions in the second stepp and finally receive a confirmation mail from the web application whit his credentials in the last step. I can't access the last step, because of the ModelState.isValid method that I use to handle validations, and which can't perform properly if I define some properties as [Required], but don't put them on the first view. As the replies to those questions remain in a couple of choices, I've thinked that I may use some nullable bool? for in order to avoid validation issues, but know that it's not the proper way. Are there someone who would like to help me find a way to extend my validation to those three steps ? Thanks in advance and sorry for my english, I'm not a native speaker.

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  • Easy Transfer from a dead computer

    - by Nathan DeWitt
    I had a computer that electrocuted me and the company sent me a new one. The hard drive from the old computer works fine and is in my new computer. I would like to transfer my files from the old drive to the new one, preferably using Easy Transfer (old & new computers were Win7). When I go through the Easy Transfer wizard, it assumes my old computer is running and that I can run a process to backup all my data to a single file. However, in my case I have the system drive in my new computer and want to pull the data off it. I would like to avoid rebooting the old computer, to avoid damage to myself or my data. I would like to avoid booting into the old system drive, as my new hardware is significantly different and I imagine I'll run into some missing hardware issues. What's the easiest way to get my data off this drive?

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  • MEF, IServiceProvider and Testing Visual Studio Extensions

    - by Daniel Cazzulino
    In the latest and greatest version of Visual Studio, MEF plays a critical role, one that makes extending VS much more fun than it ever was. So typically, you just [Export] something, and then someone [Import]s it and that's it. MEF in all its glory kicks in and gets all your dependencies satisfied. Cool, you say, so let's now import ITextTemplating and have some T4-based codegen going! Ah, if only it was that easy. Turns out by default, none of the VS built-in services are exposed to MEF, apparently because there wasn't enough time to analyze the lifetime, initialization, dependencies, etc. for each one before launch, which makes perfect sense. You don't want to blindly export everything now just in case. There's also the whole VS package initialization thing which in this version of VS is not so transparently integrated with the MEF publishing side (i.e. a MEF export from a package can get instantiated before its owning package, and in fact, the package can remain unloaded forever and the export will continue to be visible to anyone)....Read full article

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  • Suggested HTTP REST status code for 'request limit reached'

    - by Andras Zoltan
    I'm putting together a spec for a REST service, part of which will incorporate the ability to throttle users service-wide and on groups of, or on individual, resources. Equally, time-outs for these would be configurable per resource/group/service. I'm just looking through the HTTP 1.1 spec and trying to decide how I will communicate to a client that a request will not be fulfilled because they've reached their limit. Initially I figured that client code 403 - Forbidden was the one, but this, from the spec: Authorization will not help and the request SHOULD NOT be repeated bothered me. It actually appears that 503 - Service Unavailable is a better one to use - since it allows for the communication of a retry time through the use of the Retry-After header. It's possible that in the future I might look to support 'purchasing' more requests via eCommerce (in which case it would be nice if client code 402 - Payment Required had been finalized!) - but I figure that this could equally be squeezed into a 503 response too. Which do you think I should use? Or is there another I've not considered?

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